Universal joint

ABSTRACT

There are provided two shafts which can be faced in different directions one of which ends including a first fork with a crosspiece joining it with a second fork. The second forks are mechanically joined to each other by means of an axial displacement device comprising a first bearing plate that is formed integrally to the second fork of one of the shafts, an intermediate plate and a second bearing plate. The first bearing plate is provided with columns formed integrally thereto and to the second bearing plate. The intermediate plate comprises through bores that receive said columns ( 19, 20, 21 ), and a column formed integrally thereto and to the second fork of the other shaft. The relative clearance between said first bearing plate and the intermediate plate defines the possible displacement between the forks of the respective shafts.

[0001] Drive devices socalled universal joints are known intended todrive a rotating movement of two shafts arranged at different relativepositions to enable the angular displacement therebetween.

[0002] Said devices are typically used in the automotive field to driverotating movement to the wheels when they are driving and driving wheelsat a time, as to steering columns of the motor vehicles where it is notpossible to drive the movement by means of a monolithic longitudinalshaft, especially due to the particular geometry of the interior of thevehicle where the various mechanical parts in the steering assembly haveto be fitted and to work.

[0003] The improved universal joint provided with the present inventionis intended to drive rotating movement of two shafts capable of facingin different directions. To achieve this, one end of said shafts isprovided with a first fork having holes intended to receive the ends ofthe arms of a crosspiece. Said crosspiece hingedly joins said first forkwith the ends of a second fork.

[0004] The main feature of the present invention is that the secondforks of the shafts are mechanically joined to each other by means of anaxial displacement device. Said axial displacement device is designed totake up the effects of an external shock which could give rise tointerferences on the operation of the mechanical system and even tofailures or damages of severe consequences.

[0005] In a specific application for steering columns, the use of theuniversal joint as the one herein described makes possible toadvantageously prevent movements from being transmitted from the rack tothe steering column of the vehicle thus isolating the columns from thesteering assembly.

[0006] Another advantage of the present invention is the possibility tochange the clearance of the shaft forks which notably facilitatesassembly thereof thanks to the play existing therebetween, this allowingthe mechanical assembly to be adapted in a more convenient way, alwaysassuring a perfect driving.

[0007] More specifically, the axial displacement device of the universaljoint of the present invention comprises a first bearing plate that isformed integrally to the second fork of one of the shafts. The axialdisplacement device also comprises an intermediate plate that isparallel to said first bearing plate. Finally, there is provided asecond bearing plate that is parallel thereto.

[0008] The first bearing plate of the axial displacement device isprovided with guiding and fastening columns. Said columns are formedintegrally by one of their ends to the first bearing plate. In turn,these columns are also formed integrally to said second bearing plate bytheir opposed ends.

[0009] The mentioned intermediate plate is provided with through boresadapted to receive said guiding and fastening columns thereacross. Saidintermediate plate also has a column formed integrally thereto by an endand, by the other end, to the second fork of the other shaft.

[0010] With the disclosed configuration, the relative clearance betweensaid first bearing plate and said intermediate plate defines adisplacement between the forks of the respective shafts which providesthe above mentioned advantages. Thus, in case of a contingent externalstress, the system reacts balancing it by displacing the assembly formedby the columns fixed to the intermediate plate relative to the guidingand fastening columns fixed to the two bearing plates. Hence, there is arelative movement between the forks of the shafts that enables to takeup any movement caused by an external agent to the driving systemitself, with low sliding load and high twisting stiffness.

[0011] The invention also envisages the possibility of providing aflexible protective element that covers the axial displacement devicesurrounding it so that the mechanical parts are isolated from dust, dirtand other external agents that could affect the dynamic performance ofthe universal joint. By way of an example, said protective element maybe a rubber tube surrounding the device and that, in turn, allows themovement of the elements in an appropriate way.

[0012] Additionally, the axial displacement device of the universaljoint of the present invention is provided with biasing means tending tokeep the clearance between the forks of the respective shafts in thecase of an external stress thus allowing taking up of load in thecollapse.

[0013] Preferably, the first bearing plate of the axial displacementdevice comprises three cylindrical guiding and fastening columns formedintegrally thereto by one of their ends. Their opposed ends are screwfixed to said second bearing plate. The guiding and fastening columnsmay be hollow bars to reduce the weight of the assembly.

[0014] The intermediate plate is provided with friction bushes housedinto said through bores to allow the controlled passing of the guidingand fastening columns thereacross and to enhance sliding thereof.Alternatively, the through bores of the intermediate plate have asurface finishing suitable to allow snugly passing of said columns.Thanks to said features, torque transmission with no play and with avery low sliding stress are achieved.

[0015] On the other hand, the column formed integrally to theintermediate plate is formed with a cylindrical member fixed theretopassing through a bore of said second bearing plate.

[0016] The first bearing plate, the intermediate plate or the secondbearing plate may have a quadrilateral or triangular profile withrounded vertexes, even though there is also the possibility of includingany appropriate profile.

[0017] With a joint as the one herein described it is possible to obtainan effective drive means having a great simplicity and low cost due tothe preferred geometries of the plates, as stated above.

[0018] Further details and features of the present invention will beapparent from the following description, which refers to theaccompanying drawings that schematically represent the preferreddetails. These details are given by way of example, which refer to apossible case of practical embodiment, but it is not limited to thedisclosed details; therefore this description must be considered from aillustrating point of view and without any type of limitations.

[0019]FIG. 1 is a perspective view of the universal joint according tothe present invention;

[0020]FIG. 2 is an elevational view of the universal joint of FIG. 1;

[0021]FIGS. 3 and 4 are end views of the forks corresponding to thedriving shafts according to the view of the assembly shown in FIG. 2;and

[0022]FIG. 5 is a plan view of the universal joint of FIG. 1.

[0023] A detailed list of the various parts cited in the present patentapplication is given below:

[0024] (1) first fork corresponding to driving shaft;

[0025] (2) extension of the first fork corresponding to driving shaft;

[0026] (3) housing of the first fork corresponding to driving shaft;

[0027] (4) first fork corresponding to driven shaft

[0028] (5) extension of the first fork corresponding to driven shaft;

[0029] (6) housing of the first fork corresponding to driven shaft;

[0030] (7) bores of the forks of the driving shaft;

[0031] (8) bores of the forks of the driven shaft;

[0032] (9) ends of the arms of the crosspiece of the driving shaftforks;

[0033] (10) ends of the arms of the crosspiece of the driven shaftforks;

[0034] (11) crosspiece of the driving shaft forks;

[0035] (12) crosspiece of the driven shaft forks;

[0036] (13) second fork corresponding to the driving shaft;

[0037] (14) second fork corresponding to the driven shaft;

[0038] (15) axial displacement device;

[0039] (16) first bearing plate;

[0040] (17) intermediate plate;

[0041] (18) second bearing plate;

[0042] (19, 20, 21) guiding and fastening columns;

[0043] (22, 23, 24) ends of the guiding and fastening columns;

[0044] (25, 26, 27) opposed ends of the guiding and fastening columns;

[0045] (28) central cylindrical column;

[0046] (28 a) central bush of the second bearing plate to enable passingof the central cylindrical column;

[0047] (29) end of the central cylindrical column;

[0048] (30) opposed end of the central cylindrical column;

[0049] (31) protective element of the axial displacement device;

[0050] (32) biasing means;

[0051] (33) bushes of the intermediate plate to enable passing of theguiding and fastening columns;

[0052] (s) clearance between the first bearing plate and theintermediate plate.

[0053] The assembly shown in the figures comprises a first fork (1)adapted to receive a first shaft, or driving shaft, which it has notbeen shown in the drawings for the sake of clarity. The end of thedriving shaft is housed into an extension (2) of said first fork (1)where there is provided a housing (3) suitably adapted therefor.

[0054] At the opposed end of the assembly there is provided anotherfirst fork (4) that similarly houses a second shaft, or driven shaft,which also has not been shown in the drawings for sake of clarity. Theend of said driven shaft is housed in a similar way in an extension (5)of the first fork (4) where there is a housing (6) adapted therefor.

[0055] The first forks (1, 4) of both shafts are provided with bores (7,8) where the ends (9, 10) of the arms of respective crosspieces (11, 12)mutually joining in a hinged way the corresponding first forks (1, 4)with the ends of the second forks (13, 14) of the driving and drivenshafts are housed.

[0056] Both second forks (13, 14) are mechanically joined to each otherby means of an axial displacement device generally denoted by referencenumeral (15) in the figures attached in the present specification.

[0057] Said axial displacement device (15) has the role of establishinga given play between the clearance of the second forks (13, 14) in orderto take up the effects of an external shock which could adversely affectthe normal operation of the mechanical system, as to facilitate theassembly of the shafts thanks to said play established therebetween.

[0058] Said axial displacement device (15) essentially comprises a firstbearing plate (16) formed integrally to the second fork (13) of thedriving shaft, an intermediate plate (17) parallel to the first bearingplate (16) and a second bearing plate (18) parallel thereto.

[0059] The first bearing plate (16) comprises three guiding andfastening columns (19, 20, 21) formed integrally by their ends (22, 23,24) in said first bearing plate (16). Said guiding and fastening columns(19, 20, 21) are also formed integrally to the second bearing plate (18)by their opposed ends (25, 26, 27). Fastening of the ends (25, 26, 27)may be by screwing, whilst the guiding and fastening columns (19, 20,21) may be solid bars or hollow bars to reduce the weight of theassembly.

[0060] The intermediate plate (17) of the axial displacement device (15)has through bores allowing the passing of the guiding and fasteningcolumns (19, 20, 21) thereacross. The intermediate plate (17) has acentral cylindrical column (28) formed integrally thereto by an end (29)and formed integrally, by the other end (30), to the second fork (14) ofthe driven shaft. Said central column (28) pass across a bore thathouses a bush (28 a) in the second bearing plate (18) of the axialdisplacement device (15).

[0061] Referring FIG. 2 of the drawings, relative clearance (s) betweenthe first bearing plate (16) and the intermediate plate (17) define therelative displacement between the forks (13, 14) of the respectiveshafts. By way of an example, the effective play that it has been foundfor a typical application of a vehicle steering column is about 34 mm.However, this maximum clearance may have any value depending upon themechanical requirements of the joint as well as the application that isto be intended, possibly up to 100 mm in some cases, or even more.

[0062] To isolate the moving mechanical parts from dust, dirt and otherexternal agents, a flexible protective element (31) covering the axialdisplacement device (15) surrounding it may be provided. By way of anexample, a rubber tube (31) surrounding the bearing plates (16, 18) andthe intermediate plate (17) may be provided in such a way that is itpossible the relative movement thereof in an appropriate way.

[0063] Movement of said elements can be controlled through biasing means(32) in the form of a compression spring in order to keep the clearance(s) between the first bearing plate (16) and the intermediate plate (17)from collapse stresses, taking them up in an effective way.

[0064] Sliding of the guiding and fastening columns (19, 20, 21) throughthe intermediate plate (17) is carried out by means of bushes (33)housed into the through bores of said plate (17). If bushes are notprovided, the through bores of said intermediate plate (17) must have aninner surface finishing suitable to allow snugly passing of the threecolumns (19, 20, 21) and to achieve a torque transmission with no playand with a very low sliding stress.

[0065] In the preferred embodiment of an improved universal jointaccording to the present invention shown in the figures, the firstbearing plate (16), the intermediate plate (17) and the second bearingplate (18) have a triangular profile with rounded vertexes. In thevicinity of the vertexes of said triangular shape defining the plates(16, 17, 18) said guiding and fastening columns (22, 23, 24) arearranged.

[0066] The universal joint as the one herein described allows taking upstresses of an external origin to the system balancing it by displacingthe assembly formed by the column (28) with the intermediate plate (17)relative to the guiding and fastening columns (19, 20, 21) and thebearing plates (16, 18). As stated above, this is due to the firstbearing plate (16), the fastening columns (19, 20, 21) and the secondfork (13) of the driving shaft which are formed integrally to eachother, whilst the central column (28) is formed integrally to theintermediate plate (17) and to the other second fork (14). Hence, thereis a relative movement between the forks (13, 14) of both shafts thatadvantageously enables to take up any movement caused by external agentsto the driving system.

[0067] Once having been sufficiently described what the present patentapplication consists in accordance to the enclosed drawings, it isunderstood that any detail modification can be introduced asappropriate, provided that variations may alter the essence of theinvention as summarised in the appended claims. In this sense,arrangement of any number of guiding and fastening columns according tothe requirements of the joint is falling within the inventive scope ofthe present invention. On the other hand, the profile of the firstbearing plate, the intermediate plate or the second bearing plate willbe any profile suitable to the requirements of the assembly.

1 ^(a)—“IMPROVED UNIVERSAL JOINT” to drive rotating movement of twoshafts which can be faced in different directions, the end of saidshafts being provided with a first fork (1, 4) having bores (7, 8) tohouse the ends (9, 10) of the arms of a central crosspiece (11, 12)hingedly joining each first fork (1, 4) with a second fork (13, 14),characterised in that said second forks (13, 14) of each shaft aremechanically joined to each other by means of an axial displacementdevice (15) comprising a first bearing plate (16) that is formedintegrally to the second fork (13) of one of the shafts, an intermediateplate (17) that is parallel to said first bearing plate (16) and asecond bearing plate (18), said first bearing plate (16) being providedwith guiding and fastening columns (19, 20, 21) formed integrallythereto by one of their ends (22, 23, 24) and formed integrally to saidsecond bearing plate (18) by their opposed ends (25, 26, 27), saidintermediate plate (17) comprising through bores adapted to receive saidguiding and fastening columns (19, 20, 21) thereacross and saidintermediate plate (17) being also provided with a column (28) formedintegrally thereto by an end (29) and being formed integrally, by theother end (30), to the second fork (14) of the other shaft, the relativeclearance (s) between said first bearing plate (16) and saidintermediate plate (17) defining the displacement between the forks (1,4, 13, 14) of the-respective shafts. 2 ^(a)—“IMPROVED UNIVERSAL JOINT”as claimed in claim 1, characterised in that said axial displacementdevice (15) is provided with biasing means (32) tending to keep theclearance (s) between the first bearing plate (16) and the intermediateplate (17) in the case of an external stress. 3 ^(a)—“IMPROVED UNIVERSALJOINT” as claimed in claim 1, characterised in that the first bearingplate (16) comprises three cylindrical, guiding and fastening columns(19, 20, 21) formed integrally thereto by one of their ends (22, 23,24), their opposed ends (25, 26, 27) being screwed to said secondbearing plate (18). 4 ^(a)—“IMPROVED UNIVERSAL JOINT” as claimed inclaim 3, characterised in that said three cylindrical, guiding andfastening columns (19, 20, 21) are hollow. 5 ^(a)—“IMPROVED UNIVERSALJOINT” as claimed in claim 1, characterised in that said intermediateplate (17) is provided with bushes (33) housed into said through boresto allow the controlled passing of said guiding and fastening columns(19, 20, 21) thereacross to obtain an improvement on sliding with noplay and wear strength. 6 ^(a)—“IMPROVED UNIVERSAL JOINT” as claimed inclaim 1, characterised in that said through bores of said intermediateplate (17) have inner surface finishing allowing snugly passing of saidguiding and fastening columns (19, 20, 21). 7 ^(a)—“IMPROVED UNIVERSALJOINT” as claimed in claim 1, characterised in that the column (28)formed integrally to said intermediate plate (17) is formed with acylindrical member fixed thereto passing through a bore of said secondbearing plate (18). 8 ^(a)—“IMPROVED UNIVERSAL JOINT” as claimed inclaim 1, characterised in that at least any of the first bearing plate(16), the intermediate plate (17) and the second bearing plate (18) hasa quadrilateral profile with rounded vertexes. 9 ^(a)—“IMPROVEDUNIVERSAL JOINT” as claimed in claim 1, characterised in that at leastany of the first bearing plate (16), the intermediate plate (17) and thesecond bearing plate (18) has a triangular profile with roundedvertexes. 10 ^(a)—“IMPROVED UNIVERSAL JOINT” as claimed in claim 1,characterised in that it comprises a flexible protective element (31)that covers the axial displacement device (15) surrounding it.